---
title: "Vector distance functions"
sidebarTitle: "Vector Distance"
description: "cosine_distance, distance, exact_distance and inner_product: per-row vector distance, and the ORDER BY rewrite into vector search."
icon: ruler
keywords: ["distance", "cosine_distance", "exact_distance", "inner_product", "vector search", "sql", "scalar function"]
availability:
  embedded: unavailable
  enterprise: available
---

```text
cosine_distance  distance  exact_distance  inner_product
```

<Warning>
Distance functions can evaluate arrays per row. Some deployment versions also
recognize `ORDER BY distance(vector, query_vector) LIMIT k` over a table scan
and plan it as vector search, with indexed or flat search as appropriate.
Where available, `exact_distance` evaluates distance without that rewrite.
Confirm the functions supported by your deployment and inspect SQL
[`EXPLAIN`](/sql/dql/explain); the function name alone does not guarantee an
index-backed plan. See [SQL vector search](/basics/sql#no-vector-sql).
</Warning>

A third, optional argument is a comma-separated options string, and only
`distance` and `exact_distance` accept one; `cosine_distance` and
`inner_product` are plain two-argument functions. `metric` selects `l2`
(default, alias `euclidean`), `cosine`, or `dot`. `nprobes` and `use_index`
only affect `distance`, since it's the only one of the two that the
index-search rewrite applies to in the first place -- `exact_distance` is
never rewritten into an index search, so passing it `use_index`/`nprobes`
does nothing; use a plain `distance` call with `use_index=false` to force a
flat scan instead:

<CodeGroup>
```sql SQL icon="database"
SELECT id FROM documents
ORDER BY distance(embedding, ARRAY[0.1, 0.2, 0.3], 'metric=cosine,nprobes=20')
LIMIT 10

-- Force a flat scan, bypassing the index:
SELECT id FROM documents
ORDER BY distance(embedding, ARRAY[0.1, 0.2, 0.3], 'use_index=false')
LIMIT 10
```
</CodeGroup>

## What to read next {#next}

<CardGroup cols={2}>
  <Card title="SQL vector search" icon="magnifying-glass" href="/basics/sql#no-vector-sql">
    Server-version requirements and the supported `ORDER BY` query forms.
  </Card>
  <Card title="EXPLAIN" icon="diagram-project" href="/sql/dql/explain">
    Confirm whether a query planned as an index-backed vector search.
  </Card>
</CardGroup>